Having owned every generation of GM truck--often multiple examples--- from the AD series to the K2XX, with the exception of the GMT900........
The old original 2 speed Power Glides--with scheduled maintenance--were good for 75k miles or so before they gave out. And yes, racers are running 2000 hp with Power Glides but they are built from the ground up to race, and the Power Glides have LOTS of room inside them to install bodaciously big, heavy duty parts to hold up.
The Turbo-Hydramatic 350--with scheduled maintenance--was good for 100k before they broke (having broke a few, I know this). The TH350 is a similar design to the Power Glide.
The 4L60E (we'll just skip through the 700R and 4L60) is a TH350 with overdrive installed in the tail--and with scheduled maintenance--generally last 150k miles (all four 4L60E I've owned that broke, did it between 155k-160k miles). The electronic versions probably last longer than the non-electronic 4 speed trans precisely because of torque management ability.
In other words the GM "light duty" auto trans have improved their lifespan over the years. It's important to note any hydraulically driven automatic transmissions are inherently hard on themselves, and it doesn't matter what brand or design we consider.
It would have been nice to have all the GM half tons come with 4L80E's, but it is all about cost---and cost is why half tons are more popular than 3/4 or 1 tons. Nor is it fair to compare a less expensive trans to a more expensive trans. We can just blame the original buyers of these half tons of being cheapskates........
It's also important to note that todays Turbo Diesel "HD" trucks have much more extensive torque management program because even my vaunted Allison transmission (and drivetrain) can't handle all the torque at once my 06 Sierra TD makes. And today's TD's in the HD trucks are a LOT more powerful and can grenade any part of the drivetrain in a heartbeat without torque management.
Equally important, the introduction of the Vortec motors upped the ante quite a bit in the hp and torque game. The 5.7 L31 made 330 ft/lbs of torque, and in comparison the awesome original LT-1 small block made about 370 ft/lbs of torque. The LT-1 was a full blown hotrod motor in the muscle car era, the L31 is a everyday workhorse motor.
The GMT400's were not only an improvement, they were such an improvement over earlier generations of trucks the Chevy and GMC GM400 series of pickups and SUV's combined were easily the most popular trucks sold during the late 90's.
Surprise this morning. PCM arrived at my door. Popped that right in. Noticeably more power! Not tons, but noticeable. Shifting is precise and not harsh or hard. While PCM was out like I noted earlier I added Corvette servo so hard to say which of these is having more of that impact. When weather clears I’m onto transmission fluid exchange, new filter and new aluminum pan w/Moroso 93104 gasket. Also, got GlowShift Temp guage installed!
